Solid surface modification, a well-studied area in surface chemistry and interface engineering, is showing promise in being applied broadly in industry and daily life. The surface property of a solid can be changed after modification of the surface and a series of properties such as absorption, wettability, dispersion, etc. Among the above surface properties of a solid, wettability is of great importance. Wettability is mainly determined by two indispensable factors: the chemical property and the geometrical morphology. The wettability of the solid surface can be changed by changing its roughness.
Currently in this art, there are a variety of methods for modifying the surface of the polymer materials, which may be generally classified as chemical and physical modification methods.
(1) Dipping Modification
In this method, the surface property of the polymer materials is improved by dipping the polymer materials into a treatment solution for oxidization. The disadvantages of using particular treatment solutions include the short life span of such solutions and sometimes repeated dipping.
(2) Photochemical Modification
In this method, the wettability and stickiness of the surface of the polymer materials can be improved through a chemical change induced by the exposure to ultraviolet irradiation.
(3) Surface Graft Modification In this method, plasma, an ultraviolet or chemical agent is used to generate grafting sites on the surface of the polymer materials; then the polymer materials are placed into monomers for grafting.
(4) Radiation Modification
In this method, the polymer materials are subjected to ionization, excitation and the generation of free radicals caused by the radiation in order to break bonds and make cross-links, or the generated free radicals polymerize with other monomers to achieve a surface modification.
(5) Coating Method
In this method, the surface property of the polymer materials is improved by coating some inorganic oxides thereon at a low temperature through a vacuum deposition process.
(6) Plasma Surface Modification
In this method, a large amount of active particles contained in the plasma such as electron, ions, and atoms and molecules in the excited state act on the surface of the polymer materials to induce complex physical and chemical changes causing etching, cracking and polymerizing, and generating a large quantity of free radicals or some polar groups; thus improving the surface property of the polymer materials. The plasma surface modification is advantageous in that only the superficial surface layer of the materials is modified without changing the main body and various surfaces can be modified by using suitable kinds of plasma gases. However, it is disadvantageous in that the degrading effectiveness of plasma exists.
The above methods have main drawbacks as follows during changing of surface wettability of polymer materials:
(1) Wastes are produced, which will pollute the environment, during the chemical modification process;
(2) Radioactive pollutions exist during the radiation modification process;
(3) The vacuum evaporation and plasma surface modification need expensive devices and have a complex operation process.